This invention relates to a running state control system for a vehicle.
As a running state control system for a vehicle, there is known a traction control system for preventing lowering of acceleratability owing to a spin of a driving wheel by an excessive driving torque during an acceleration. In the traction control system, a spin quantity of the driving wheel (difference between a wheel speed of the driving wheel and that of a driven wheel) is detected to control an engine output or brake force (namely, to decrease the engine output, or to increase the brake force) to the wheels so that the spin quantity of the driving wheel reaches to a target quantity.
It has been proposed in Japanese Patent Application Laying Open Gazette No. 64-30869 that in order to ensure a stability in lateral direction of the vehicle, the traction control system is provided with steering angle detecting means for detecting a steering angle of a handle and the target quantity for the brake control is lowered when the vehicle is activated and the handle is steered.
Another known running state control system is an automatic adjusting suspension (hereinafter referred to it as AAS). The AAS controls each damping ratio of shock absorbers respectively provided at a front right, front left, rear right and rear left of a vehicle according to the steering angle, namely the ratios are controlled to be large (soft) during a straight run and to be small (hard) during a turn. As a result, the vehicle is prevented from rolling during a turn.
In driving techniques of a vehicle, there are a slalom run, which the vehicle runs with the handle alternatively steered to the right and left, and a counter steering for recovering the vehicle state by steering the handle in a reverse direction of the vehicle, not in a forward direction in case the rear part of the vehicle turns sideways out from a running line.
The vehicle having the above traction control system or AAS has problems upon such the driving techniques.
Namely, in case of the vehicle with the traction control system in which the target quantity for a traction control by an engine output is set high during a strait run and set low during a turn so as to enhance the stability in lateral direction during a turn, when the steering angle becomes zero during the handle is steered, for example, from right to left, the engine output abruptly exceeds because of the high target quantity.
Also, the vehicle having the AAS has another problem that when the steering angle becomes zero, each damping ratio of the shock absorbers abruptly becomes large.